Obviously, we should try to invent a synthetic higgs boson so the universe makes sense again.posted by mccarty.tim at 10:02 AM on September 14, 2011 [2 favorites]

That article is terrible.

This isn’t to say the search is over. Quite the contrary, a 95% probability of exclusion still leaves a 5% chance that the Higgs is indeed in the predicted energy ranges and simply hasn’t been observed yet.

This is flat out incorrect. It doesn't tell you anything about the chances that the Higgs is in the remaining range. If the higgs exists, there's a 100% chance it's in that range.posted by empath at 10:02 AM on September 14, 2011 [5 favorites]

Higgs Boson walks into church. Priest says tells it to get out. Higgs Boson: "But without me how can you have mass?"posted by exogenous at 10:03 AM on September 14, 2011 [104 favorites]

This means that physicists are 95% certain that the Higgs Boson does not exist in those energy ranges, and worse, those are the energy ranges in which we expected to find the Higgs.

This is also incorrect. There's a super-symmetric model that predicts 5 different higgs bosons in that range.posted by empath at 10:04 AM on September 14, 2011

It means the Higgs boson has more than might have been expected in common with everyday macroscopic objects such as my god-damned keys.posted by Wolfdog at 10:04 AM on September 14, 2011 [26 favorites]

So, then, what does it mean if we don’t find the Higgs at all?

I guess it means we don't have mass.

Seriously, though. We seem to be screwing mass up. From the missing (so far) Higgs to dark matter. We don't understand something.posted by DU at 10:05 AM on September 14, 2011 [13 favorites]

Pointing out that there’s a possibility that the Higgs Boson may not exist and that there are other theories around what a Higgsless universe would look like is a fairly controversial statement.

Except that I'm not sure that this is true. Science thrives on disproving. Proving that the Higgs doesn't exist would be more exciting and significant than proving that it does.

I think my favorite bit of Higgs Boson trivia is about how it got the name "The God Particle":

It wasn't even Lederman's choice. "He wanted to refer to it as that 'goddamn particle' and his editor wouldn't let him," says Higgs.

That is such a better name! It's so evocative of the problem it presents. "Ugh, this goddamn particle! Where the fuck is it! DAMMIT!"posted by Doublewhiskeycokenoice at 10:07 AM on September 14, 2011 [24 favorites]

It's really not even really the particle they're searching for, they're trying to prove the existence of the Higgs Mechanism, which is basically what keeps neutrons stable enough for atoms to form.

The higgs mechanism requires a higgs field which couples with the electroweak field, which limits the range of W and Z bosons that causes neutrons to decay. If it wasn't for that, neutrons would immediately decay into protons (among other things) and the universe would be a much different place.

The experiments at LHC are basically just trying to plunk a small enough area with enough energy to set the higgs field vibrating, which would create a 'particle' called the higgs boson, but the particle itself isn't the important thing, the higgs field is.posted by empath at 10:18 AM on September 14, 2011 [3 favorites]

This is a misguided rebuttal. You introduced a conditional.
p(Higgs_in_range | Higgs_exists). The former statement had no such presumption.posted by stonepharisee at 10:19 AM on September 14, 2011 [4 favorites]

In the olden days, scientists played with stuff and drew conclusions. In the newendays (my son coined that word at age 5) all the mysterious stuff is too small or too big or too hot or too simple or too complex or too invisible, so scientists extrapolate the math and physics, make assumptions, then look for the stuff that will verify their assumptions. It's getting more deductive, like religion. So this is bound to happen. Ultimately, science is not about alliances or bets or beliefs, so it's great when scientists are befuddled. It only leads to better science.posted by weapons-grade pandemonium at 10:19 AM on September 14, 2011 [5 favorites]

Maybe the Higgs only exists and operates when you don't attempt to directly observe it? I call this the "Mario's Ghost" theory.posted by naju at 10:20 AM on September 14, 2011 [8 favorites]

It means the Standard Model is wrong and we've got new physics to discover.

This is not a bad answer. This is how science works. If you do the experiment knowing what the answer will be, it's not an experiment. It would also be very cool, because the the Standard Model has been very good so far.posted by eriko at 10:23 AM on September 14, 2011 [2 favorites]

It could be kind of bad from a "willingness of the public to fund huge projects" POV, though.posted by DU at 10:25 AM on September 14, 2011 [2 favorites]

This is a misguided rebuttal. You introduced a conditional.
p(Higgs_in_range | Higgs_exists). The former statement had no such presumption.

If I told you I lost my cellphone somewhere in my house, and we searched 19 out of 20 rooms without finding it, would you say that there's a 95% chance that it never existed? I mean sure there is some small chance that I'm a crazy person and invented the fact that I ever had a cellphone, but it's not a 95% chance.

That's the situation we're dealing with with the higgs. Everything we know about theoretical physics from the past few decades points to the existence of the higgs field. The odds of it existing don't go down every time we look somewhere and don't find it.posted by empath at 10:26 AM on September 14, 2011 [2 favorites]

As a wiser man than me once said, "If we knew what it was we were doing, it would not be called research, would it?"posted by BigHeartedGuy at 10:28 AM on September 14, 2011 [4 favorites]

I guess it depends on the definition of "olden days." I'm always amazed at the history of modern chemistry, for example, which is pretty perfectly described by "all the mysterious stuff is too small or too big or too hot or too simple or too complex or too invisible, so scientists extrapolate the math ... make assumptions, then look for the stuff that will verify their assumptions."posted by muddgirl at 10:28 AM on September 14, 2011 [5 favorites]

DU: The public is perfectly willing to fund huge and ridiculous huge projects if you frighten them.

I'm really in the "I hope we're missing something basic about mass" camp. I also hope that whatever it is I'm hoping that we're missing leads us to one, or several, of the more awesome sci-fi technologies.posted by Slackermagee at 10:34 AM on September 14, 2011 [6 favorites]

And the Higgs Boson is using it to call you FROM INSIDE THE HOUSE! Okay, okay, I'll go.posted by JHarris at 10:35 AM on September 14, 2011 [3 favorites]

Higgins' Boss has always been missing. Robin Masters is kind of a joke character who is never seen. But if he really did go missing, Magnum would find him.posted by George_Spiggott at 10:36 AM on September 14, 2011 [9 favorites]

Just to note: if the Higgs is not found in this energy range, it really only rules out the simplest Standard Model Higgs. There are (as mentioned in the Not Even Wrong post) many other alternatives which are only really different in that they are less palatable or less complicated in important ways. I think most theorists (other than maybe Weinberg and Salam) were really hoping not to find the Higgs at this energy range as it really opens up the door to far more exotic ideas.

As far as this being a potential failure of modern physics, well, it really is almost impossible to state exactly how right the Standard Model is. I mean, we can calculate certain quantities to such unbelievable accuracy that it would make your head spin. If this bit about the Higgs particle turns out to be more complicated than originally anticipated, that doesn't make the rest of the model retroactively wrong. It just means that it's field of applicability is slightly less large than we originally thought.

Quantum Mechanics didn't make Newtonian physics wrong, it just put limits on it. Similarly, relativity puts limits on the usefulness of Classical physics, but it does not retroactively make it not work.

Physics is not fundamentally about perfect, ultimate truths. It is a collection of incredibly successful models, each with their own defined ranges of usefulness. Sometimes we find that certain models don't work very well in certain places that we had hoped they would work, and other times we find new models that make us rethink how we were applying the other models, but in the end, it's models all the way down.posted by artichoke_enthusiast at 10:36 AM on September 14, 2011 [8 favorites]

This means that physicists are 95% certain that the Higgs Boson does not exist in those energy ranges, and worse, those are the energy ranges in which we expected to find the Higgs.

This is also incorrect. There's a super-symmetric model that predicts 5 different higgs bosons in that range.

It is true that the (SM) Higgs has been excluded in it's most likely location. If you use the entirety of our physics measurements to predict where you would expect to see the Higgs, you get a number around ~100 GeV. Which was excluded by LEP in the 90s. This has been a dirty little secret that Higgs hunters don't really talk about too much.

Not finding the Standard Model Higgs would generally be considered a good thing. If we found a single SM Higgs with a reasonable mass, it would give us no new information; it would essentially just tell us that the Standard Model works, which we already know. But to learn what's beyond the SM, we need to see some non-SM physics, and the Higgs is the best hope for that.

Like empath says, the most likely non-SM theory is supersymmetry, which predicts 5 Higgs. Two of those particles would be neutral scalar particles like the Standard Model Higgs, which essentially cuts the likelihood of seeing a neutral Higgs at any given mass in half (yikes, gross oversimplification). So if we don't see enough Higgs-like events to discover the SM higgs, there could still be neutral Higgses kicking around out there. There's just less events to see because they're happening at different masses.

Personally, I'm still hoping for a low mass Higgs to make my Masters thesis worthwhile, but if you put a gun to my head I'd predict we won't see a Standard Model Higgs at all.posted by auto-correct at 10:37 AM on September 14, 2011 [1 favorite]

Like empath says, the most likely non-SM theory is supersymmetry, which predicts 5 Higgs.

And, also points us in the direction of an explanation for dark matter. I think supersymmetry is my favorite outcome.posted by empath at 10:41 AM on September 14, 2011

I always assumed Dan Brown named it.

Renowned theoretically-predicted elementary particle Higgs Boson broke electroweak gauge symmetry while giving mass to a gauge boson, frustratingly out of reach of world-famous particle physicist Dr. Michael Parr of the prominent Large Hadron Collider in Geneva, Switzerland, a city near one of the largest lakes in Europe.posted by villanelles at dawn at 10:43 AM on September 14, 2011 [17 favorites]

Also, something a lot of people don't talk about is that there is really compelling evidence that the Standard Model require some kind of new (massive, scalar) particle to be self consistent. There are interactions where the numbers only add up if there's an additional boson -- not necessarily the Higgs, but the Higgs fills the roll nicely.

This is the reason that scientists have bet the farm that we'll see something new at LHC energies. We're basically left with the options that

a) there is a Higgs, and its mass is < 1 TeV
b) there is some other new particle with a mass < 1 TeV
c) there is no new particle and our most basic assumptions about perturbation theory and the way particles interact with each other are wrong.

All of which are interesting outcomes. There is essentially no null-result in this search.posted by auto-correct at 10:45 AM on September 14, 2011 [2 favorites]

Info in recent years indicates that supersymmetry is also not exactly coming out smelling of roses lately in LHC data. That said, it's certainly not taking the beating that the Standard Model Higgs seems to be getting.

I'd love to see supersymmetry come through, but that's just because it's such a tantalizingly fun idea.posted by chimaera at 10:45 AM on September 14, 2011

If I told you I lost my cellphone somewhere in my house, and we searched 19 out of 20 rooms without finding it, would you say that there's a 95% chance that it never existed?

That's not what they said, though. Rather they are saying that they sampled enough points in each of those 19 rooms to say that there is a 95% chance that it is not in any of those (19) rooms. That means there is A) a 5% chance that it is in one of those rooms and B) some probability that it is in the 20th room, or doesn't exist at all (extending the metaphor, you could say they don't have a key to the 20th room and can't test it at this point)

Here is what you quoted, read more carefully:

This isn’t to say the search is over. Quite the contrary, a 95% probability of exclusion still leaves a 5% chance that the Higgs is indeed in the predicted energy ranges and simply hasn’t been observed yet.

Seriously, though. We seem to be screwing mass up. From the missing (so far) Higgs to dark matter. We don't understand something.

Can a physicist explain what mass, energy, space and time "really are", in relation to each other - i.e. our best current metaphors - in relatively straightforward way in a paragraph or three? I often wonder if these models we've made have become far too complicated, epicycles revolving on deferents offset by equants, more and more tweaks and layers. The standard model in particular just seems ... obtuseposted by crayz at 10:48 AM on September 14, 2011

Can a physicist explain what mass, energy, space and time "really are", in relation to each other - i.e. our best current metaphors

How can you explain what something 'really is' using a metaphor?posted by delmoi at 10:51 AM on September 14, 2011 [1 favorite]

What these scientists and our theoretical phone-losing colleagues need to remember is that a lost or undiscovered item is always, always, in the last place you look. So all they need to ask themselves is, "Where is the last place we would look?" The Higgs, if it exists, is bound to be there.posted by BrotherFeldspar at 10:52 AM on September 14, 2011 [2 favorites]

Rather they are saying that they sampled enough points in each of those 19 rooms to say that there is a 95% chance that it is not in any of those (19) rooms

We have seen many impressive new physics limits set at this conference. But, have we ever truly believed in the models that are being pushed away? Z-prime, CMSSM, split SUSY, to name a few? I myself certainly never believed in these. Take Z-prime. In spite of what you may have heard, this is a completely unmotivated extension of the SM. It solves nothing of its problems and has nothing to do with Naturalness. Same for split SUSY, anathema to Naturalness. CMSSM is the only victim on the list for which I feel sorry, but we can’t give up on SUSY just because this straightjacketed version of it failed.

Another early casualty has been the Large Extra Dimensions scenario. But again, this was hardly a bona fide solution to the hierarchy problem. The mechanism which cuts off the Higgs mass quadratic divergence has not been concretely specified. It’s only because the idea was so original that we ever gave it the benefit of the doubt. Now with LHC limits on the (4+n)-dimensional Planck scale already a factor two above the Tevatron limits, it’s basically gone. The truth is, apart from SUSY, there are only two other motivated scenarios for TeV-scale physics: strong EWSB and Composite Higgs. I mentioned some of the signals expected in these models. Unlike CMSSM, they typically require much higher luminosity to be seen.

This is making it sound like there's already somewhat muted disagreement over the credibility of the "theory space" being tested by the LHC. Is this just standard model stalwarts refusing to give up? If the LHC doesn't find anything, will the argument be that we need a more powerful collider to test more exotic extensions of the status quo theory?posted by crayz at 10:57 AM on September 14, 2011

Can a physicist explain what mass, energy, space and time "really are", in relation to each other - i.e. our best current metaphors - in relatively straightforward way in a paragraph or three? I often wonder if these models we've made have become far too complicated, epicycles revolving on deferents offset by equants, more and more tweaks and layers. The standard model in particular just seems ... obtuse

In our defense, we've tried to publicize the fact that 4 simultaneous 24 hour days rotate within the same 24 hour rotation of Mother Earth, but for some reason no one believes us.posted by auto-correct at 10:58 AM on September 14, 2011 [15 favorites]

Basically, all particles have a set of properties, such as spin, charge, color, flavor, etc, and a lot of particle interactions can be though of as particles (or a set of particles) actually being absorbed at one spot in space and then being re-emitted as a different particle or set of particles, where the totals of those properties are conserved, usually mediated by a force particle -- for example, a photon with the right momentum can spontaneously create an electron/positron pair or vice versa.

The different forces can be thought of as mediating different kinds of changes -- for example, the weak force (mediated by w bosons) causes a quark to change flavor which causes neutrons to decay into protons, electrons and neutrinos.

The strong force (mediated by gluons) causes quarks to change color, and there are other examples.

These transformations all seem to have do with certain symmetries in the equations that govern the actions of these particles.

One thing that we haven't found is a force that allows fermions (matter like electrons, quarks, etc) to run into bosons.. (force carriers like photons).

Supersymmetry is a proposed theory for how that could happen, which suggests that all particles have supersymmetric partners which are the opposite type -- for example, there's a partner for the photon that's a fermion called a photino, and a partner for the electron that's a boson called a selectron.

It basically doubles the number of particles that can exist, some of which are electrically neutral but would have mass, and could explain dark matter.posted by empath at 10:58 AM on September 14, 2011 [2 favorites]

The best argument against the Higgs is that elementary linear scalar fields are problematic (since not asymptotically free) and esthetically displeasing (not geometrical and constrained by symmetries, so lead to lots of undetermined parameters, mainly for the Yukawas that determine the masses of all fermions).

Can a physicist explain what mass, energy, space and time "really are", in relation to each other - i.e. our best current metaphors - in relatively straightforward way in a paragraph or three?

The relationship between time and energy is that since the laws of physics are 'time-invariant' (the laws of physics don't change over time) energy is conserved, since energy is what governs the laws of motion.

You're right, I misread what he was saying..posted by empath at 11:04 AM on September 14, 2011

This is making it sound like there's already somewhat muted disagreement over the credibility of the "theory space" being tested by the LHC. Is this just standard model stalwarts refusing to give up? If the LHC doesn't find anything, will the argument be that we need a more powerful collider to test more exotic extensions of the status quo theory

To say that there's disagreement about what theories we should be looking for beyond the Standard Model (BSM) is an understatement. There is tacit agreement that a minimal supersymmetric model is a good thing to look for since it requires no great theoretical leaps and would solve some current problems. Beyond that, everyone and their dog has their own idea of what to look for. What people consider "natural" or "elegant" is wildly subjective. This is a feature. We live in interesting times.posted by auto-correct at 11:08 AM on September 14, 2011 [1 favorite]

"Design me a fine large hadron collider, bean" is an anagram for "If Higgs real, Leon Lederman can be ordained."posted by TreeRooster at 11:08 AM on September 14, 2011 [2 favorites]

To say that there's disagreement about what theories we should be looking for beyond the Standard Model (BSM) is an understatement.

Yeah, I read a lot of physics blogs, and it's like some of them aren't even speaking the same language -- like string theory vs quantum loop gravity people.posted by empath at 11:12 AM on September 14, 2011

Life goes on, that's what happens.

Little ditty about CERN and Fermilab
Two subatomic physics labs, one's in Switzerland
Banging on some particles at high TeV's,
Jackie don't know which hand is which if it violates CP.

A lot of people stand to gain whopping big grants for developing the next theories, and the means to test them.posted by KirkJobSluder at 11:34 AM on September 14, 2011

That's it! The Higgs Boson is only present in homeopathic quantities. Which not only explains why you can't detect it but how incredibly effective it is.posted by George_Spiggott at 11:34 AM on September 14, 2011 [6 favorites]

Fuck the Higgs - I'm still awaiting the ever elusive new Boards of Canada album!posted by symbioid at 11:43 AM on September 14, 2011 [2 favorites]

A lot of people stand to gain whopping big grants for developing the next theories, and the means to test them.

lol nanowhopping grants to develop the theory, whopping grants to do the experiments.posted by ozomatli at 11:45 AM on September 14, 2011 [2 favorites]

So, then, what does it mean if we don’t find the Higgs at all?

That science works as advertised?posted by Thorzdad at 11:54 AM on September 14, 2011

No matter, no mind I guess. Wait...oh shit, we don't exisposted by codswallop at 11:55 AM on September 14, 2011

Also - you guys, damnit... Everytime I think I'm grokking shit about particle physics, you have to explain things, and the Higgs is something I completely misunderstand. I'm gonna have to go back and re-read some materials. Ugh.posted by symbioid at 12:03 PM on September 14, 2011

The statistical argument here seems off, and I suspect that ExtremeTech got it badly wrong in their paraphrase of Scientific American, as does the "rooms" idea.posted by KirkJobSluder at 12:19 PM on September 14, 2011

With the Rooms analogy above, you're presuming the existence of the phone, and finding out it's not in certain rooms makes it more likely that it's in one of the remaining rooms.

This doesn't really apply to what's happening with the Higgs Boson.posted by ged at 1:06 PM on September 14, 2011 [1 favorite]

Higgins' Boss has always been missing. Robin Masters is kind of a joke character who is never seen

I hope nobody gets mad at me for spoiling it but Higgins was Robin Masters.posted by Ad hominem at 1:55 PM on September 14, 2011

To use a better analogy, you're looking for the Scottish Plaid Muddy River Catfish. You have a theory about where it lives, what it looks like, and what bait you need to catch it. And you figure that with the right bait and a good rod, you should be able to catch a fair number of them. So you get in your boat and start testing the theory.

And after a year or so of this, most of the time you catch nothing, some of the time you catch less extraordinary fish, and on a few occasions, you catch something that might be a Scottish Plaid Muddy River Catfish, but probably is an off-color Norwegian Blue Parrotfish.

Now, since science is a probabilistic inference you can't say that your theory is absolutely wrong unless you've personally checked the passports of every fish that lived in the river. So what you do is a statistical test. You open up SPSS, SAS, or R, punch in your predicted numbers and your experimental numbers, make some big assumptions about what kind of probability distribution you want to test against, and you say something like:

"I can say with a 95% level of confidence that my theory of how to catch the Scottish Plaid Muddy River Catfish is wrong. Further research is needed to..."posted by KirkJobSluder at 1:58 PM on September 14, 2011 [1 favorite]

I hope they don't find it. I like it when physicists are surprised.

So you want it to find them? Then leave it to the Russian scientists.posted by davejay at 2:14 PM on September 14, 2011 [1 favorite]

The green band is the likelihood that the Higgs will be found at a given mass. Closer to zero = more likely. The grey bands are the regions excluded by previous experiments with 95% confidence. I'm pretty sure that the Tevatron band has become thicker since this figure was made.posted by auto-correct at 2:15 PM on September 14, 2011 [1 favorite]

In the olden days, scientists played with stuff and drew conclusions. In the newendays (my son coined that word at age 5) all the mysterious stuff is too small or too big or too hot or too simple or too complex or too invisible, so scientists extrapolate the math and physics, make assumptions, then look for the stuff that will verify their assumptions.

I think this mischaracterizes science all along. It has always been a sequence in which observations are made, a model is formulated to explain those observations, and new observations are taken to challenge the model. If the model fails, a new or modified model is created to take account of the new observations. Rinse, Repeat. It has always dealt in observations of the effects of hidden truths, be they forces, tiny particles, or invisible essences.

Also, I totally am going to steal your 5-year-old's word.posted by Mental Wimp at 2:25 PM on September 14, 2011

What's all this I hear about the Higgs bosom? That's a terribly sexist concept for physics I must say! I --

What? Higgs what, now? Oh!

Never mind.

It was either this or my companion-particle-Higgs-boson's-mate gag, and that one is starting to smell.posted by Guy_Inamonkeysuit at 2:56 PM on September 14, 2011

It has always been a sequence in which observations are made, a model is formulated to explain those observations, and new observations are taken to challenge the model. If the model fails, a new or modified model is created to take account of the new observations. Rinse, Repeat. It has always dealt in observations of the effects of hidden truths, be they forces, tiny particles, or invisible essences.

Well, there is a branch of physics which is concerned with working out the physics of rather abstract mathematical or geometric concepts to see what kind of universe they would generate, which may or may not be at all related to the actual universe. The value in that is when we observe something in experiment that matches with that abstract math, we already have the tools at hand to interpret it.

That seems to be most of what string theory/m-theory is right now-- just systematically working out all the possible universe one could create with the various types of string theories, and waiting to see if an experiment helps them narrow down some of the parameters.

That kind of pie in the sky theorizing has paid off many times before. Reinmann and Gauss, etc, worked out most of the geometry of General Relatively before Einstein was even born, for example. If we didn't have theoreticians laying out the ground work, interpreting new experimental data would be a lot more difficult than it is. If einstein had to invent non-euclidean geometry himself, he may not have ever gotten around to General Relativity.

I think, in a sense, that math is physics, and that no matter how abstract the math, there seems to be some application to physics, somewhere.posted by empath at 3:34 PM on September 14, 2011 [1 favorite]

Well, there is a branch of physics which is concerned with working out the physics of rather abstract mathematical or geometric concepts to see what kind of universe they would generate, which may or may not be at all related to the actual universe.

empath, I'm aware of that process. Generally, this work is done by mathematicians, and not specifically for physics, but more to see where it takes things. I'm not sure it can be called science, per se, but rather it is developing tools that science might one day use to explain newly observed phenomena. Math has always been sort of iconoclastic, even though others often find it useful, sometimes astoundingly so.posted by Mental Wimp at 4:03 PM on September 14, 2011

I'm not sure it can be called science, per se, but rather it is developing tools that science might one day use to explain newly observed phenomena.

I have to agree with empath that while absolutely lots has changed about science over the last couple hundred years, the fundamentals are still the same.

In Newton's age, he would dream up crazy ideas about light, then tinker around with double slits and see what happened. These days theorists dream up crazy ideas about particles, and experimentalists tinker around with colliders. I think the roles are much more regimented and specialized, and the "tinkering" can't be done on the coffee table anymore, but the way science works is still the same.posted by auto-correct at 5:25 PM on September 14, 2011

What these scientists and our theoretical phone-losing colleagues need to remember is that a lost or undiscovered item is always, always, in the last place you look.

I went to India to find myself. Turns out I was in the last place I looked.posted by kersplunk at 6:29 PM on September 14, 2011

To elaborate on auto-correct's link, what that plot is saying is that the mass that the Standard Model wants the Higgs to be at is already completely ruled out, and has been for over a decade since the LEP-II experiment finished. "Wants" here means "would increase consistency with precision experiments, in which the Higgs wasn't directly discovered, but small effects from the Higgs would have been apparent."

So this sky-is-falling hysteria from the science press seems way out of left field to me - the SM Higgs has been in trouble for a long time. Yes, a lot of the parameter space is ruled out now, no we haven't seen anything yet. This is called "doing science." To be honest, I think some people got way too attached to their pet theories in the 30 years when no one could tell them they were wrong, and as soon as some of the likely ones got knocked off, the panic button got hit. As someone who entered the field recently, I don't have a horse in that race, so I'm not concerned yet.

The real worry is that no sign of anything like supersymmetry has been seen yet. We built the LHC to find the Higgs, and there were various no-lose theorems saying we would either find the Higgs or find what else does its job. I'm not sure whether those theorems still hold with the reduced run parameters of the LHC, but I think with a long enough run that will eventually happen. So finding the Higgs, or finding what goes on at 2 TeV of energy when probability breaks down without the Higgs (as in, the probability of particles scattering goes above 100%) is going to occur. If it doesn't, well, we just found a place where probabilities sum to over 100%, and I have first dibs on building a casino there.

What the not-so-secret hope of every theorist has been is that we'll find the reason that the 2 TeV (that's the energy equivalent of about 2000 proton's worth of energy) is so special. This gets into the idea of naturalness and hierarchy, which are really interesting concepts that are sort of at the core of what a lot of thought in the last 30 years of theoretical physics gets into.

Every quantum field theory gets quantum corrections (loops, they are referred to, due to the fact that in Feynman diagrams - the way we do shorthand for calculations - they look like, you guessed it, loops). It turns out that these corrections tend to be calculated in terms of the highest energy scale in your theory, the cutoff scale we'll call Lambda. This is the scale at which you've postulated that things fundamentally change, and you're thus justified in throwing up your hands waiting for more data instead of continuing the calculation.

Now, we know how to calculate these quantum corrections for things like couplings (how strongly particles interact with each other) and mass. With fermions - spin 1/2 particles like electrons and quarks - it turns out that the loop corrections to the mass are 1) proportional to the uncorrected "bare" mass itself and 2) proportional to the logarithm of Lambda.

1) makes sense because massless fermions must stay massless. See my post in the last thread about the Higgs here for an idea about why (basically, mass for fermions actually ties two different particles together. So, if there is no mass without loops then there aren't two particles that can be appropriately linked, and so there's nothing for loops to link together). 2) is much more subtle, but what it's saying is that the mass of an fermion is really not that concerned about the scale at which your theory goes to hell.

An electron, for example, has a mass of 511 keV. That is the physical mass: the sum of the bare (non-loop) mass and the loop corrections. Even if the loop corrections had a cutoff Lambda of the highest scale imaginable, the Planck scale at 10^19 GeV (when there's enough energy around to form into a black hole), the correction would only be 10%. Logs are crazy like that. Thus, we don't have to "fine-tune" the bare and loop corrections against each other. The bare mass is presumably some number close to 511 keV (its not a measurable quantity though), and then you get a small correction from the loop. All is right in the world.

Now lets look at a fundamental scalar particle, like the Higgs (note: no other scalars are known to exist in nature). It's loop corrections are independent of the tree-level mass, and go like Lambda. So, if the Higgs is under 2 TeV in mass, and the correction is on the order of 10^19 GeV, there is a massive fine-tuning issue. Imagine you and I pick two 6 digit numbers, and then we take the larger and subtract the smaller. The odds of us getting a 1 digit number are tiny: we'd have to very carefully tune the two original big numbers to get a small one. That's the problem with the Higgs mass, except that the two numbers you're cancelling against each other are presumably 19 digits long.

(Technically, the tuning is worse than this sounds, since the fundamental property for scalars is mass^2, not mass. So you're tuning to 10^6 parts in 10^38, not 10^3 parts in 10^19). That's the Naturalness problem: how does the Universe "protect" the hierarchy between the Higgs scale (1000-ish GeV) and the Planck scale (10^19 GeV).

Supersymmetry solves this by doubling the number of particles that run around in the loops. By taking every particle and giving it a super-partner of the opposite spin-statistics (spin-0 gets spin-1/2, spin-1 gets spin-1/2, etc), you get identical contributions to the loop corrections, but with the opposite sign. So that huge correction you originally had goes away (small number + big number - the same big number = small number). Of course, we don't see those superpartners, so they can't be as light as their "normal" counterparts (there is no photino with zero mass to hang out with the massless photon). So supersymmetry must be "broken:" moving the partners up a bit in mass. Of course, this makes the cancellation in the loops imperfect; and so the partners can't be too heavy or else we have the fine-tuning problem again. Too heavy in this case means, again you guessed it, 1 TeV or so. So if we don't see supersymmetry at the LHC (and we haven't yet), then this beautiful idea goes right out the window.

There are other ideas for fixing this problem; one other leading candidate is technicolor, which basically says that the higgs is a composite particle made up of fundamental fermions bound together with a very powerful new force of nature. The analogy is the proton: made of quarks bound together by the strong nuclear force (thus "technicolor" for the new force instead of "color" for the strong force). The problem here is that, while we can't calculate strongly interacting properties very well (the Feynman diagram technique breaks down; you'd have to sum an infinite series of diagrams to get the right answer), our best estimations of the theory make predictions that have been proven to be incorrect. However, if we wave our wand and utter the magic words "non-perturbative corrections" then maybe Technicolor is still ok. It's a really elegant idea in any case, and we know nature picked this solution once already (it's why physicists don't worry about why the strong-force scale - 1 GeV - was not quantumly corrected up to the Planck scale).

(the 3rd main candidate is extra dimensions, which brings the Planck scale down to a TeV. It's basically killed by the LHC already, so we'll skip that)

Regardless, if we don't see something soon to solve the hierarchy and naturalness problems (and ironically, most solutions are easier to find than the Higgs itself), then either there's something very subtle we haven't thought of (likely), or the Universe just doesn't give a fuck about cancelling two very big numbers to get a small number. That latter option is conceivable, but very, very, VERY unsatisfying to those of us who think about these problems. It also gives us no handle on where to look next for interesting new physics, which would be really depressing.

All that said, supersymmetry is not dead yet (like the Monty Python sketch). Most of the benchmark models are out, but they were not a great cross-section of whats possible to begin with. So, like everything else, we won't see anything until we do, and then there will be a mad scramble to figure out what the hell is going on. It will be unlike anything the field has seen since the 1970s. So I'll take the optimistic view for now that things are about to be really interesting; at worst, if I'm wrong, the rest of the physicists and I will have decades to sit upon the ground and tell sad stories about the death of tuning. So why start the pity-party early?posted by physicsmatt at 7:55 PM on September 14, 2011 [17 favorites]

what is loop correction?posted by delmoi at 9:04 PM on September 14, 2011

I love the comment by exogenous.....I want to tell my friend in China, but how the heck am I ever going to translate it into Chinese?posted by girdyerloins at 9:23 PM on September 14, 2011

So what would the universe look like if the Higgs boson didn't exist? If it doesn't exist, I'd have to assume the universe would look just like is does now.posted by warbaby at 10:05 PM on September 14, 2011

Have you not heard of that madman who lit a lantern in the bright morning hours, ran to the market place, and cried incessantly: "I seek Higgs! I seek Higgs!" -- As many of those who did not believe in the Higgs Boson were standing around just then, he provoked much laughter. Has it got lost? asked one. Did it lose its way like a child? asked another. Or is it hiding? Is it afraid of us? Has it gone on a voyage? emigrated? -- Thus they yelled and laughed.

The madman jumped into their midst and pierced them with his eyes. "Whither is Higgs?" he cried; "I will tell you. We have killed it -- you and I. All of us are its murderers.posted by homunculus at 11:15 PM on September 14, 2011 [1 favorite]

Why is it called "research", if they never found it before?posted by Goofyy at 11:52 PM on September 14, 2011

Because it resembles regard and regret.posted by nobody at 6:20 AM on September 15, 2011

If there was no Higgs, then the weak nuclear interaction would be very different. If the Higgs scale was enormously large (one way to interpret the phrase "no Higgs"), then the weak interaction would be even weaker than it is. Why does this matter? Well, without the weak interaction, there would be no weak-mediated nuclear decay (or the inverse processes, shutting off some nuclear fusion channels used by the Sun), so there would be limited building of heavy elements, no type-II supernovae (to seed the primordial clouds of gas that built our solar system), and so (it seems) no us. (There's an alternative view on this, see http://arxiv.org/abs/hep-ph/0604027, but I disagree with some of their conclusions, in particular, the seeding issue)posted by physicsmatt at 7:14 AM on September 15, 2011

So finding the Higgs, or finding what goes on at 2 TeV of energy when probability breaks down without the Higgs (as in, the probability of particles scattering goes above 100%) is going to occur.

Or it's the reset button for the universe.posted by Mental Wimp at 8:26 AM on September 15, 2011

PhysicsMatt: Would it be enormously unsatisfying to say that the big numbers cancel because of the anthropic principle, that we're only around to puzzle about this sort of thing because we're in a universe where they balance?posted by Joe in Australia at 4:14 PM on September 18, 2011

Tags

Share

About MetaFilter

MetaFilter is a weblog that anyone can contribute a link or a comment to. A typical weblog is one person posting their thoughts on the unique things they find on the web. This website exists to break down the barriers between people, to extend a weblog beyond just one person, and to foster discussion among its members.